Onychomycosis is a fungal infection of the nail matrix, bed, or plate. Such fungal infections of the nail are difficult to treat, and recurrence is common. The reported incidence of the disease is from 2% to 14%, but the actual incidence is probably much higher. Dermatophytes, candida spp. and nondermatophytic molds (such as Scytalidium dimidatum and Scopulariopsis spp.) can infect nails and result in four major clinical presentations. The most common clinical presentation is distal and lateral subungual onychomycosis (DLSO), followed by total dystrophic onychomycosis (TDO), superficial white onychomycosis (SWO) and proximal subungual onychomycosis (PSO) which are often AIDS-associated.
Nails infected by onychomycosis become opaque, thickened, fragile and brittle. In addition, the growth of the fungus can actually lift the nail plate up and off the nail bed, causing pain for the patient. Eventually, loss of the entire nail may result from the disease.
Treatment methods for nail fungus have included surgical or chemical removal of the infected nail and treatment of the exposed nail bed with topical antifungals. Such treatments must be continued until the nail grows out, which can take six months or more. Although the cure rate for such surgical treatments is generally high, the procedure is painful and can result in permanent nail loss.
Other attempted treatment methods have included the use of disinfectant nail polish removers, such as is described in U.S. Pat. No. 5,063,049 to Billings. The composition disclosed in Billings combines a carrier or solvent made up of butyl acetate, ethyl acetate and isopropyl alcohol, combined with a fungicide of parachlormetaxylenol, and a bactericidal element consisting of thymol crystals.
Other inventors have utilized topical solutions. For example, U.S. Pat. No. 5,696,105 to Hackler discloses a topical creme containing mometasone furoate as a vasso constrictor.
Still other inventors have combined topical solutions with medicated devices. For instance, U.S. Pat. No. 5,464,610 to Hayes, Jr. et al., discloses the use of salicylic acid in a plaster preparation. This method allows for a continuous delivery of the active ingredient. U.S. Pat. No. 5,346,692 to Wohlrab et al. describes another method of continuously providing a topical agent to the infected nail. In Wohlrab, an antimycotically active substance and urea are combined with nail polish.
Despite prior attempts to treat onychomycosis, contentional topical treatments of nail infections has proven to be ineffective and oral antifungals suffer from various deficiencies, including safety and cost concerns. In addition, the topical application of known solutions generally must be continued for at least 10 weeks, and often must be regularly applied for an entire year. This is because the relative thickness of the nail plate inhibits penetration of topical applications. Additionally, compositions that are topically applied frequently are worn off of the infected area before they can penetrate the nail. Furthermore, recurrence of the infection is common once treatment ceases. Therefore, existing topical applications have proven less than satisfactory in treating nail infections.
Attempts at treating nail fungus have also been made using orally administered anti-fungal agents, but at significant economic and safety costs. The efficacy of such orally administered drugs, however, is limited due to the poor circulation of blood in the nail bed. As a result, treatment via oral methods requires high drug dosages over long periods of time. Such high dosages can have adverse side effects, and removal of the infection is often only temporary. As with known topical solutions, recurrence of the infection is common once the anti-fungal agents are no longer being administered. Because of hepatotoxicity and drug-drug interactions, these oral agents have played a limited role in the treatment of onychomycosis. Further, with the high drug costs, required laboratory testing and frequent office visits, many third party payers are limiting reimbursement for treatment to certain patients (diabetics, peripheral vascular diseases, history of lower extremity cellulitis, etc.).
In view of the above-described limitations of existing methods for the treatment of nail infections, a need exists for a new method for removing onychomycosis and other infections of the nail. The present invention addresses this need by providing a method and composition for reliably treating such infections from the nail without causing adverse side effects.